Dear ( the teacher's name ):
I am going to have an exam of getting the accounting certificate .so it seems that I can't take the next lesson with you.I am sorry about it. Thank you for being so understanding.
yours,
(your name)
Dear ( the teacher's name ):
I am going to have an exam of getting the accounting certificate .so it seems that I can't take the next lesson with you.I am sorry about it. Thank you for being so understanding.
yours,
(your name)